A new study published by Science reconstructs global temperatures further back than any previous study, going back a whopping 11,300 years to study historic global temperature changes in the Earth's atmosphere. The most notable study prior to this was Penn State University’s 1999 study which used tree rings to show a massive uptick in temperatures in the 20th century, when humans began dumping large amounts of greenhouse gases into the atmosphere. The new study uses objects collected from more than 70 different sites, primarily fossilized ocean shells that have been unearthed by oceanographers. Chemical tracers in the shells of fossilized shells link closely to temperature changes in the environment.